COMPOSITION AND USE

Abstract: A toner resin composition comprising a toner resin and a negative charging charge control agent (CCA) which is a di- or trivalent metal salt of a naphthalene oxy-carboxylic acid wherein the hydroxy group and carboxylic acid group are attached to adjacent carbon atoms of an aromatic ring. The CCA is preferably the zinc, aluminium or iron salt of 3-hydroxy-2-naphthoic acid.

Description: COMPOSITION AMD USE The present invention relates to the use of di- or trivalent metal salts of a naphthalene oxy-carboxylic acid compound containing a hydroxy group and a carboxylic acid group attached to adjacent carbon atoms of an aromatic ring as a negative charging charge control agent and to compositions containing such a salt. It has already been proposed to use anionic metal complexes as charge control agents (hereinafter referred to as CCA's) in electro-reprographic imaging processes. For example, EP 162,632 discloses toner compositions containing 2:1 cobalt complexes of simple azo chromophores and more recently US 5,143,809 discloses polyester resin toner compositions containing an anionic 2:1 zinc complex of an aromatic oxy-carboxylic acid compound. None .of these compounds are entirely satisfactory as CCA's. Those disclosed in EP 162,632 are coloured molecules which limits their use and as with those disclosed in US 5,143,809 they are charged molecules which can interfere with their formulation in toner compositions or toner-resin compositions. Furthermore, industry is constantly requiring simpler and more effective compounds " as CCA's. We have now found that simple metal salts of a naphthalene oxy-carboxylic acid compound containing a hydroxy group and a carboxylic acid group attached to adjacent carbon atoms of an aromatic ring are suitable as a negative-charging CCA in a toner composition for electro-reprographic imaging processing. According to the invention, there is provided a toner resin composition comprising a toner resin and a negative charging CCA which is a di- or trivalent metal salt of a naphthalene oxy-carboxylic acid wherein the hydroxy group and the carboxylic acid group are attached to adjacent carbon atoms of an aromatic ring. Preferably the salt has a formula I. wherein X is optionally substituted C- L .-.-alkyl which may be linear or branched, alkenyl, hydroxy, halogen, nitrile, nitro, amino, substituted amino, aryl, alkaryl, aralkyl, acyl, acyloxy, alkoxy, alkoxy carbonyl, alkyl or aryl sulphonyl, carbonamide or sulphonamide; p is 0 to 6; M is a divalent or trivalent metal cation; and n is 2 or 3. The group X is selected to enhance the compatibility of the salt in the toner resin. When X is alkyl, it is preferably methyl, ethyl, isopropyl, t.butyl, amyl, hexyl, nonyl, decyl or dodecyl. When X is halogen, it is preferably fluorine, bromine and especially chlorine. When X is substituted amino, it is preferably C-^-alkylamino such as diethylamino, dibutylamino, hexylamino and 2-ethylhexylamino. When X is aryl or aralkyl it is preferably phenyl, benzyl or ethylphenyl. When X is acyl, acyloxy, alkoxy or alkoxycarbonyl it preferably contains a C x . l2 -alkyl moiety. Preferably, p is 0,1 or 2, and especially 0. When p is not 0, X is preferably alkyl, and it is also preferred that X is located in the 5 and/or 7 position of the naphthalene ring. Examples of suitable naphthalene oxy-carboxylic acids are 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 8-hydroxy-l- naphthoic acid, l-hydroxy-2-naphthoic acid and derivatives thereof such as 5,7-ditertiarybutyl-3-hydroxy-2-naphoic acid. When M is a divalent metal cation, the metal is preferably one from groups 2a, lb or 2b of the Periodic Table by Mendeleef as published for example in the Handbook of Chemistry and Physics, published by The Chemical Rubber Company. When M is a trivalent metal cation, the metal is preferably one from either group 8 or group 3a of the Periodic Table. When the metal is divalent it is preferably calcium or magnesium and especially zinc. When the metal is trivalent it is preferably iron or aluminium. The toner resin is a thermoplastic resin suitable for use in the preparation of toner compositions. A preferred toner resin is a styrene or substituted styrene polymer or copolymer such as polystyrene or styrene-butadiene copolymer. It is especially preferred that the toner resin is a styrene-acrylic copolymer such as a styrene-butyl methacrylate copolymer. Other suitable toner resins are polyesters, especially alkoxylated bis-phenol based polyester resins such as those described in US 5,143,809, polyvinyl acetate, polyalkenes, poly(vinyl chloride), polyurethanes, polyamides, silicones, epoxy resins and phenolic resins. Further examples of these and other resins are given in the book "Electrophotography" by R M Schafert (Focal Press); UK 2,090,008, US 4,206,064 and US 4,407,924. The toner resin composition may contain more than one CCA of formula I. The CCA is present in the composition from 0.1 to 12%, preferably from 0.5 to 10% and especially from 1 to 3% by weight of the total composition. The toner resin composition may also contain a dyestuff or pigment as colourant. Thus, according to a further feature of the invention there is provided a toner resin composition as hereinbefore defined which further comprises a colourant. The colourant is preferably a pigment such as carbon black, metallised phthalo- cyanines, quinacridones, pe ' rylenes, benzidines, nigrosines, anilines, quinolines, anthraquinones, metallised lakes and pigment toners and water insoluble salts of basic dyes. The colourant may also be a water soluble basic dye, especially a triphenylmethane dyestuff. The toner composition may contain up to 20% colourant and especially from 3 to 10% relative to the total weight of the toner resin composition. The toner resin composition may be prepared by any method known to the art which typically involves mixing the toner resin with the CCA of formula I and optionally the colourant by kneading in a ball mill above the melting point of the resin. Generally, this involves mixing the molten composition for several hours at temperatures from 120 to 200°C, in order to uniformly distribute the CCA and colourant (if present) throughout the toner resin. The toner resin is then cooled, crushed and micronised until the mean diameter of the particles is preferably below 20μ and, for high resolution electro-reprography, more preferably from 1 to lOμ. The powdered colour toner or toner-resin so obtained may be used directly or may be diluted with an inert solid diluent such as fine silica by mixing for example in a suitable blending machine. The CCA's of formula I are prepared by any method known in the art and are conveniently made by dispersing the oxy-carboxylic acid in water and/or a hydrophilic solvent and then adding an aqueous solution of an alkali metal hydroxide in substantially stoichiometric amounts to dissolve the oxy-carboxylic acid. Stoichiometric amounts of a water soluble salt of the metal are then added and the reaction mix stirred until the reaction is complete and the metal salt of the carboxylic acid separates and is collected by normal methods known to the art, such as by filtration and washing. The formation of the alkali metal salt of the oxy-carboxylic acid and its salt with the metal M is normally effected at temperatures below 60°C, and preferably at temperature from 20 to 25°C. Mixtures of different metals may be used as the water soluble salt, but it is preferred to use single metals. Similarly, different oxy-carboxylic acids may be used simultaneously which results in CCA's having different substituents in the naphthalene ring in the CCA of formula I. It is preferred however, that only a single oxy-carboxylic acid is used. The CCA of formula I is particularly well suited for use in electro-reprographic imaging processes on account of ease of dispersability in the resin, stability to processing and high charge capacity. The zinc and aluminium salts are especially useful since they are colourless and therefore can be used with a wide range of colourants for producing different coloured toner-resin compositions. The invention is now further illustrated by the following non-limiting examples wherein all parts and percentages are by weight unless stated to the contrary. Preparation of Zinc Salt of 3-Hvdro-cy-2-Napththoic Acid (CC 1) 3-hydroxy-2-napthoic acid (27.3 parts) was stirred at room temperature in 145 cm 3 M sodium hydroxide solution plus 50 cm 3 water until the bulk of the acid had dissolved. To the above well stirred suspension was added dropwise a solution of zinc sulphate heptahydrate (20.9 parts) in about 100 cm 3 water. Further aliquots of water were added during the addition to make the mixture more stirrable. When the addition had been completed the mixture was stirred a further one hour, then filtered and the solid product washed well with water and dried at 45°C to constant weight. A yield of 32.1 parts of a solid having a melting point in excess of 300°C was obtained. By micro-analysis, the product was found to contain C 55.6% wt; H 3.9% wt; and Zn 13.5% wt. Theory for C 22 H 14 0 β Zn.2H 2 0 is C 55.6% wt; H 3.8% wt; and Zn 13.7% wt. The proportion of water was determined by Karl Fischer analysis and found to be 7.3% wt. Theory for the zinc salt of 3-hydroxy-2-naphthoic acid dihydrate is 7.6% wt. Preparation of Calcium Salt of 3-Hvdroxy-2-Naphthoic Acid (CCA 2) 3-hydroxy-2-napthoic acid (376 parts) was added to about 1.5 dm 3 of water, which was maintained at a temperature of 50°C in a 5 dm 3 beaker. The mixture was stirred and a solution of 80 parts (2 moles) of sodium hydroxide in one dm 3 of water was added in a thin stream giving a colour change from yellow to dark brown. A solution of calcium chloride dihydrate (147 parts, 1.0M) in 200 cm 3 of water was added to the stirred mixture. On completing the addition, a cream-beige solid precipitated. The mixture was stirred for three hours at ambient temperature and the solid was then filtered off and thoroughly washed with water until the filtrate was free from chloride ion. The product was dried to constant weight in an oven at 50°C. A yield of 380.22 parts of a cream coloured solid was obtained. By micro-analysis, the product was found to contain C 56.4% wt; H 4.2% wt; and Ca 8.0% wt. Theory for C 22 H 14 0 6 Ca.3H 2 0 is C 56.4% wt; H 4.3% wt; and Ca 8.5% wt. The proportion of water was determined by Karl Fischer analysis and found to be 11.4% wt. Theory for the calcium salt of 3-hydroxy-2-naphthoic acid trihydrate is 11.5% w . Preparation of Zinc Salt of 2-Hvdroxy-l-Naphthoic Acid (CCA 3) 2-hydroxy-1-naphthoic acid (10.6 parts) was stirred with 100 cm 3 of water at 50°C. A solution of sodium hydroxide (2.26 parts) in 25 cm 3 of water was added to the stirred mixture to give a dark brown solution. Zinc chloride (3.83 parts) was dissolved in 20 cm 3 of water and the solution was added to the dark brown solution. A precipitate was formed and was stirred for 30 minutes. The mixture was cooled and filtered. The precipitate was washed thoroughly with water to remove chloride ion. The solid was dried to constant weight in an oven at 50°C. A yield of 12.53 parts of solid was obtained. By micro-analysis, the product was found to contain C 55.8% wt; H3.9% w ; and Zn 13.5% wt. Theory for C 22 H 14 0 6 Zn.2H 2 0 is C 55.6% wt; H 3.8% wt; and Zn 13.7% wt. The proportion of water was determined by Karl Fischer analysis and found to be 7.6% wt. Theory for the zinc salt of 2-hydroxy-1-napthoic acid dihydrate is 7.6% w . Preparation of Zinc Salt of 1-Hydroxy-2-Napthtoic Acid (CCA 4) l-hydroxy-2-napthoic acid (47 parts) was stirred with 150 cm 3 of water at 50°C. A solution of lOg of sodium hydroxide in 100 cm 3 of water was added and a dark brown solution was formed. Zinc chloride (17.05 parts) in 25 cm 3 of water were added to the dark brown solution. A precipitate formed. The mixture was stirred for 30 minutes, cooled and filtered. The precipitate was thoroughly washed with water to remove chloride ion and was dried in an oven at 50°C. Preparation of Iron (III) Salt of 3-Hvdroχy-2-Naphthoic Acid (CCA 5) 3-hydroxy-2-naphthoic acid (30.1 parts, 0.16M) was stirred with water (200 ml) and a solution of sodium hydroxide (6.4 parts, 0.16 M) in water (65 ml) was added. After heating to 50°C, the naphthoic acid dissolved and a solution of ferric chloride hexahydrate (8.65 parts, 0.053 M) in water (15 mis) was added. The reactants were stirred at 50°C for a further 15 minutes to form the ferric salt. After cooling, the ferric salt was filtered, washed with water and dried (Yield = 19.07 parts, 53% theory). The analysis was consistent with the empirical formula FeC 33 H 21 0 9 .3H 2 0. Preparation of the Aluminium Salt of 3-hvdroxy-2-Naphthoic Acid (CCA 61 This was prepared in analogous manner to that described in Example 4 except that the ferric chloride was replaced by the molar equivalent of aluminium chloride. Analysis was consistent with the empirical formula A1C 33 H 21 0 3 .3H 2 0. EXAMPLE 1 A toner-resin was prepared by kneading at 150°C for 30 minutes in a mixture of a styrene-acrylic resin (920 parts,- HIMER TB1000) and CCA 1 (0.5 parts) . The resin was then cooled and pulverised to give an average particle size of 10 to 12μ. EXAMPLE 2 The toner-resin from Example 1 was converted into a toner composition by kneading 93 parts of the resin with carbon black (7 parts; ELFTEX 415) at 160°C for 3 hours. After cooling, the composition was ground and pulverised until the mean particals size of the composition was below lOμ. The toner-resin composition obtained is hereinafter referred to as TRC 1. EXAMPLE 3 A developer was prepared by mixing TRC 1 (10 parts) as described in Example 2 with ferrite iron particles (90 parts) having an average particle size of 40μ. The developer was found to have an initial triboelectric charge of -16μ C.gm "1 as determined by the standard 'Blow Off method described by Schein (J. App Physics, 4_ (1975) p5140 using a Toshiba TB 200 "Blow Off" machine. EXAMPLE 4 Preparation of Toner Resins Acrylic resin (300 parts; Almacryl B-1500 resin ex Image Polymers Europe, Waalwijk, Netherlands) and a metal bonate (7.5 parts) were mixed together in a Z-blade mixer for 60 minutes at between 160 and 180°C. After cooling the crude toner resin was ground and then pulverised in a mill with steel balls for 6 days until the particle size was reduced to between 5 and 20μ. EXAMPLE 5 Tribocharσe Measurement The ground toner-resin from Example 4 (0.4 parts) was mixed with an uncoated iron powder carrier (19.6 parts, RAV-270 ex Powder Technology, USA) in an aluminium tin on a roller mill for 1 hour. The developer so obtained was evaluated on a Toshiba TB 200 "Blow off" machine and the tribocharge was measured after 2, 10, 20 and 30 minutes. The results are given in Table 1 below which show that the CCA developer obtained from iron (III) and aluminium attains a higher charge than that of the zinc and calcium bonate. TABLE 1

Claims: CLAIMS 1. a toner resin and a negative metal salt of a naphthalene oxy-carboxylic acid wherein the hydroxy and carboxylic acid groups are attached to adjacent carbon atoms of an aromatic ring. 2. A composition as claimed in claim 1 wherein the CCA has the formula wherein X is optionally substituted C 1 . 12 -alkyl which may be linear or branched, alkenyl, hydroxy, halogen, nitrile, nitro, amino, substituted amino, aryl, alkaryl, aralkyl, acyl, acyloxy, alkoxy, alkoxy carbonyl, carbonamide or sulphonamide; p is 0 to 6; M is a divalent or trivalent metal cation; and n is 2 or 3 3. A composition as claimed in claim 2 wherein p is 0. 4. A composition as claimed in any one of claims 1 to 3 wherein the metal is zinc, aluminium or iron. 5. A composition as claimed in claim 1 wherein the CCA is the zinc, aluminium or iron salt of 3-hydroxy-2-naphthoic acid. 6. A composition as claimed in any one of claims 1 to 5 wherein the toner-resin is selected from polystyrene, styrene- butadiene copolymer, styrene-acrylic copolymer, polyester, polyvinylacetate, polyalkene, polytvinyl chloride), polyurethane, polyamide, silicone, epoxy resin or phenolic resin. 7. A composition as claimed in any one of claims 1 to 6 which contains 0.1 to 12% by weight of CCA relative to the weight of the total composition. 8. A composition as claimed in any one of claims 1 to 7 which further comprises a colourant. 9. A composition as claimed in claim 8 wherein the colourant is carbon black. 10. The use of a composition as claimed in any one of claims 1 to 9 in an electro-reprographic imaging process.

Inventors: CAMPBELL JAMES STANLEY, GREGORY PETER, CAMPBELL, JAMES, STANLEY, GREGORY, PETER
Applicants: CAMPBELL JAMES STANLEY, GREGORY PETER, ZENECA LTD, CAMPBELL, JAMES, STANLEY, GREGORY, PETER, ZENECA LIMITED
Application year: 1994
Main classification: G03G9
IPC codes: G03G9